Simultaneous chemiluminescence determination of citric acid and oxalic acid using multi-way partial least squares regression

A novel kinetic chemiluminescence method has been proposed for the simultaneous determination of oxalic acid (OA) and citric acid (CA). The method is based on the catalytic effect of OA and CA in the chemiluminescence (CL) reaction of tris(1,10-phen) ruthenium(II) with Ce(IV). In the batch mode, OA gives a broad peak with the highest CL intensity at 0.7 second, whereas the maximum CL intensity of the CA appears at about 4.7 seconds after injection of Ce(IV) solution. Based on the differential rate of the CL reaction corresponding to CA and OA and different effect of Ce(IV) concentration on the CL intensity of these substances, a three dimensional data and multi-way partial least squares (N-PLS) regression method were developed for the simultaneous determination of CA and OA. After selecting the best operating parameters, calibration graphs were obtained over the concentration ranges 4.0 x 10(-8)-2 x 10(-5) mol L-1 and 2.0 x 10(-7)-2.0 x 10(-4) mol L-1 for OA and CA, respectively. The limits of detections were 2.0 x 10(-8) mol L-1 for OA and 1.0 x 10(-7) mol L-1 for CA. Relative standard deviation (RSD) of the method for 11 times simultaneous determination of 1.6 x 10(-6) mol L-1 of OA and 3.2 x 10(-6) mol L-1 of CA were 7.5% and 2.9%, respectively. The proposed method was successfully applied to the determination of the mixtures in synthetic samples, stain removers and anti-varroa mite formulations.